Previously, an air intake apparatus, which distributes air to cylinders of an internal combustion engine, is known.
For example, JP2006-97650A teaches an air intake apparatus, in which a surge tank and each cylinder are communicated with each other through a primary intake passage and a secondary intake passage, which have different passage lengths, respectively. The passage length of the secondary intake passage between the surge tank and the corresponding cylinder is shorter than that of the primary intake passage. The air intake apparatus increases a volumetric efficiency of the intake air by inertial supercharging of the intake air by opening and closing a variable intake valve, which is provided in the secondary intake passage, based on the engine speed of the internal combustion engine.
Furthermore, this air intake apparatus includes a resonator valve, which is placed between the surge tank and a resonator and includes an outer tube and an inner tube. In this resonator valve, when the inner tube, which is communicated with the surge tank, is rotated, a size of an opening of a slit, which is formed in the outer tube, is adjusted. In this way, the air intake apparatus adjusts a resonance frequency of the resonator, which is communicated with the slit of the outer tube, to increase a volumetric efficiency of the intake air by the resonance effect.
The air intake apparatus of JP2006-97650A is constructed such that a shaft, which forms a rotatable shaft of the variable intake valve, and a shaft, which forms a rotatable shaft of the inner tube of the resonator, are driven synchronously through gears and a lost-motion mechanism. The two shafts are driven by a single actuator to open and close the variable intake valve and the resonator valve. Therefore, the structure of the air intake apparatus is complicated, and the number of the components is increased. As a result, the manufacturing costs may possibly be increased, and the reliability may possibly be deteriorated.
Furthermore, slide friction between the outer tube and the inner tube of the resonator valve and slide friction of the gears and the lost-motion mechanism may possibly cause an increase in a required torque, which is required to rotate the two shafts. Therefore, a high power actuator may be required.